The poultry industry carries out the hatching of more than 8.3 million birds each week in the United States. This hatching procedure commences with the collection of eggs from a henhouse environment, the eggs being taken from the nest and positioned in a plurality of trays or flats. These trays may, for example, be placed within wheeled carts which are then delivered to a hatchery. At the hatchery, the carts and trays therewithin are positioned within relatively large incubators and there they remain generally in darkness and under carefully controlled conditions of humidity and temperature, for an interval usually amounting to about 21 days and 6 hours, at which point the operators "pull the hatch." The hatched chicks then are delivered to the "field" where they are fed over about a seven week interval at which point they are ready for market. A hen generally will lay about 100-200 eggs in its seven month economically reproductive lifetime of which only about 90% are deemed "settable" under current practice.
The 10% not considered "settable" are too small or too large for cost effective production. The chicks which are hatched from small eggs (less than 50 grams) are unsatisfactory for large scale bird production, their small size causing them to have a delayed growth pattern which generally is considered uneconomical for high volume production. As a consequence, the eggs of small size usually are sold off rather than hatched, for example, at a very low price level of about 10.cent. per dozen. On the other hand, hatchable eggs of adequate size have a value of about $2.50 per dozen at the time of this writing. Eggs from the later part of the reproductive cycle are again unprofitable. These eggs are normally quite large and if they hatch produce an excellent product. But frequently due to egg shell quality and innate embryological changes due to the large sizes, these eggs have a poor hatchability. These older birds cannot produce hatched chicks at a profit.
Beyond the development of incubating devices which have improved controls over temperature and humidity as well as enhanced egg capacities, very few recent advances have been made in the art with respect to the development of high quality chicks which evolve into a quality product at the termination of feed-out. Further, very little has been accomplished in terms of shortening the production cycle of fowl in commercial enterprises. Earlier investigations have determined that turning eggs during incubation prevents the embryo from sticking to the sides of the shell and that hatching time can be accelerated with the addition of heat. Concerning the latter, chicks obtained by increasing incubation temperature over what is considered optimal values are of a poorer quality.
Looking in more detail to earlier investigations, in 1939, Romanoff and Cottrell experimented with opened embryonic eggs and found that there existed an electrical potential difference between the blastoderm and yolk which could be accentuated with further development of the blastoderm. The more developed the blastoderm, the higher the electrical potential difference between blastoderm and yolk. See the following publication in this regard:
I. Romanoff, A. L. and C. L. Cottrell, 1939. Bioelectric potentials of the hen's egg. Science 90: (2342) 471-472 PA1 II. Romanoff, A. L., 1943. Simulating effects of UV radiation on bioelectric potentials of an avian egg. J. Cell Comp. Physiol. 20: 123-127. PA1 III. Shutze, J. V., J. K. Lauber, J. Kato and W. Wilson, 1962. Influence of incandescent and coloured light on chick embryos during incubation. Nature (London) 96: 594-595. PA1 IV. Shutze, J. V., 1977. Personal communication. PA1 V. Lauber, J. K. and J. V. Shutze, 1964. Accelerated growth of embryo chicks under the influence of light. Growth 28: 179-190. PA1 VI. Tamimie, H. S., 1967. Light exposure of incubating eggs and its influence on the growth of chicks. I. Brooding chicks under different light regimes. Comp. Biochem. Physiol. 21: 59-63. PA1 VII. Tamimie, H. S. and M. W. Fox, 1967. Effect of continuous and intermittent light exposure on embryonic development of chicken eggs. Comp. Biochem. and Physiol. 20: 793-799. PA1 IIX. Isakson, S. T., B. J. Huffman and P. B. Siegel, 1970. Intensities of incandescent light and the development of chick embryos in ovo and in vitro. Comp. Biochem. Physiol. 34: 299-305. PA1 IX. Siegel, P. B., S. T. Isakson, F. N. Coleman and B. J. Huffman, 1969. Photoacceleration of development in chick embryos. Comp. Biochem. Physiol. 28: 753-758. PA1 X. Coleman, M. A., A. Dumper, C. Luckner, R. A. McNabb and C. Sellers, 1971. Pigmentation-light screen on camouflage. Va. J. Sci. 22:99. PA1 XI. Cooper, J. B., 1972. Effect of light during incubation on hatchability of turkey eggs. Poultry Sci. 51: 1105-1108. PA1 XII. Walter, J. H. and R. A. Voitle, 1972. Effect of photoperiod during incubation on embryonic and post embryonic development of broilers. Poultry Sci. 51: 1122-1126. PA1 XIII. Walter, J. H. and R. A. Voitle, 1973. Effect of photoperiod during incubation on embryonic and post embryonic development of quail and chickens. Br. Poultry Sci. 14: 533-540. PA1 XIV. Gold, P. S. and J. Kalb, 1976. Secondry heating of chicken eggs exposed to light during incubation. Poultry Sci. 55: 34-39. PA1 XV Coleman, M. A. and C. R. McDaniel, 1975. The Effect of Light and Specific Gravity on Embryo weight and Embryonic Mortality Poult. Sci. 54: 1415-1421.
In 1943, Romanoff experimented with different energy sources, X-rays, visible light and ultra-violet radiation. It was found that the above-described electrical potential difference was greater when radiation near UV was striking the embryo. See the following publication in this regard:
Shutze, experimenting at Washington State University, determined that light would shorten the incubation period of chickens. In this work, eggs were incubated under light for varying amounts of time to study the effect of light upon eye development. However, the investigators reported that none of the monochromatic lights worked as well as white light in speeding up development. But, of monochromatic light the purple region of the spectrum was observed to have produced the most hatching acceleration. See the following publications in this regard:
In 1964, Lauber and Shutze reported that both incandescent and fluorescent light affected the length of incubation. The more time spend under either light, the shorter the incubation time. It was reported that the lights produced seemingly normal hatched chickens. See the following publication in this regard:
Another review of the effect of light upon incubation procedures was carried out in 1967. In this review, a 100 watt incandescent bulb positioned very close to the eggs being incubated was found to cause gross abnormalities, high mortality and delayed hatching. Further, chicks produced under lighted incubation did poorly in post-hatched growth. See the following publications in this regard:
In 1969 and 1970, research was carried out wherein incubating eggs were subjected to a light source present as three, 25-watt incandescent bulbs. This light was directed through a window in the shell of the egg. The investigators found no increase in mortality or abnormality with this procedure, but a decrease in hatching time. The investigators also found that light effects on shortening incubation time were most effective when utilized the first week of incubation. A noticeable acceleration of embryonic development, i.e. differentiation, occurred within 10 hours of incubation by the application of light. This was considered unusual, since it normally requires several hours for eggs to reach incubation temperature and embryonic development does not normally begin until incubation temperature is reached. It was observed that there was no significant difference in internal egg temperature attributable to the light. The investigators found that the light intensities were important in photoacceleration, with 54-108 luxes producing more somites in ovo after 24 hours. High intensity light (215-430 luxes) resulted in abnormal development both in ovo and in vitro. See the following publications in connection with the above:
In 1970, Coleman et al. reported upon the effects which light may have on the embryos from normally heavily pigmented eggs such as Japanese quail eggs. The investigation resulted in a separation of the effects on growth and differentiation of light for the first time. Embryos from pigmented and depigmented eggs incubated under lights were both larger than embryos from either type egg incubated in the dark. However, acceleration of embryonic development as well as decreased hatching times occurred only after removal of the spots (depigmentation). Embryos from depigmented Japanese quail eggs hatched 21/2 days early. White-shelled eggs developed from quails following demestication hatched much earlier than those quails which were first used experimentally. See the following publication in this regard:
Cooper observed the photoacceleration of turkey eggs as reported in 1972. Turkey eggs are normally pigmented but the spots are more dispersed than Japanese quail eggs as described above. It was reported that turkeys have increased mortality and abnormalities when incubated under light. Four, 40-watt fluorescent tubes per tray of eggs in a Robbins incubator were utilized. Turkeys which were hatched under light but incubated in the dark had improved hatchability, and the investigator attributed improved hatchability under light to added activity during the hatching period with light available for the poults. See the following publication in this regard:
Walter and Voitle reported on the effect of light during incubation for several types of birds including broiler-type chickens and quail. These investigators used one 40-watt incandescent bulb in an entire Jamesway 252 incubator. Very little effect on growth and development was recorded, but a trend toward earlier hatching for those birds incubated under the lights was noticed. No attempt was made to select uniform sized eggs and as a result standard deviations were somewhat large. The investigators also repoted no difference in post-hatch weight at eight weeks for the chicks. Further reported was an increased navel score (indicating maturity and readiness for placement) for those chicks from lighted incubation. In one experiment the investigators showed additive effects of light. Utilizing a 0-24, 12--12 and 24-0 (hour) photoperiod, it was reported that the photoacceleration of development was correlated with duration of lighting.
Gold and Kalb reported in 1976 that the "light" utilized in conjunction with incubation served only to heat the embryo, thereby increasing the temperature and decreasing the incubation period. See the following publication in this regard:
In 1975, Coleman and McDaniel reported that a light source constituted as two, 20-watt fluorescent tubes positioned over each egg tray during incubation produced a 15% heavier hatched chick in an 18 day incubation period. The birds appeared to be normal and seemed to be less susceptible to disease than their counterparts incubated in darkness. Light incubation appeared to decrease early embryonic mortality in chicks from poor quality eggs. The latter was considered to be an important observation, since as laying birds age, the size of their eggs increase, while the shell quality of those eggs deteriorates. See the following publication in this regard: